Villain is pretty unknown. 27/20/0 over 57 hands.
Flop: lots of villains nut flush draws either 3bet preflop or flat call flop so Villain should have either a set, complete air, or some combo draw like 54c 56c that didn't 3bet. Some fishy opponents could play Qx like this as well. Is there any argument for 3betting the flop against an unknown opponent? I felt that an unknown opponent at 25NL is gonna have value hands here much more often than bluffs and the average unknown 25NL opponent will call too passively if I hit my flush by the river that I can justify chasing the flush OOP. Really not scared of running into the nut flush here.

River: I doubt that villain has a worse flush here unless it was the combo draws 56c 54c (however the villains that flat these hands pre might not semi-bluff the flop, they would possibly play their draw very passively IP) or maybe QcXc but it seems more of villains range is a fishy Qx or one-street bluffs that have given up. strong Qx will probably call me here me but gladly check back. However, bluffs might try to rep the flush and fire another barrel while his combo draws (56c 45c Qcxc) i can x/r(although possibly folding out) 56c 45c.In fact, I think any half-competent Villain is folding any flush lower than Q high to a x/r OTR. Thoughts?

Poker Stars $0.10/$0.25 No Limit Hold'em - 6 players - View hand 2932040
DeucesCracked Poker Videos Hand History Converter

BTN: $36.69
SB: $81.54
BB: $27.86
UTG: $44.95
MP: $37.55
Hero (CO): $41.31

Pre Flop: ($0.35) Hero is CO with J K
2 folds, Hero raises to $0.75, BTN calls $0.75, 2 folds

Flop: ($1.85) 3 Q 7 (2 players)
Hero bets $1, BTN raises to $3.48, Hero calls $2.48

Turn: ($8.81) 4 (2 players)
Hero checks, BTN checks

River: ($8.81) 2 (2 players)
Hero bets $6.25, BTN calls $6.25

I don't understand, hand looks perfectly fine to me.

i also don't understand. Did you read my comments on the hand asking if there is merit to 3betting flop or x/r river?

3betting this flop is spew imo since it's so dry and villain's range contains mostly sets and NFDs.

Xr river is far too thin imo since there are reverse implied odds. If I'm villain with a set that (somehow) plays this way, I am folding to a river xr and calling with the nuts. but im calling a normal vbet. so xr riv is terrible. river is fine as played.

You're not going to win at showdown every time here so don't think there's something you could have done differently if he shows the nuts. Especially since this is an unknown villain, can have a heap of worse hands.

vs some nits I can fold flop and I don't hate folding here tbh since there is a lot of RIOs here. but can't really fault calling either.